The present invention relates generally to water filter carafes and more particularly to a cyst-reduction water filter carafe which can deliver substantial volumes of filtered water at relatively low (gravity-assisted) water pressures, the filtered water being substantially free of parasites and other impurities.
Gravity flow water filtration units continue to gain in popularity as consumers become concerned about the quality of available drinking water supplies. Carafe gravity flow units effectively address this concern because of their relatively low cost and perceived efficiency in removing unwanted tastes, odors, and harmful pollutants.
Operation of these units is simple and convenient. Water is simply poured into the top of the unit and is allowed to trickle through a replaceable filter cartridge to a treated water reservoir for later use. Early filter cartridges were typically packed-bed units containing carbon pellets for the removal of adsorbable/catalyzable constituents such as chlorine and organics, and ion exchange resins for the removal of metal ions such as lead. Bacteriostatic agents such as silver may also be present. More recently, cyst-reduction water filters incorporating cellular ceramic honeycomb filter elements of selectively plugged channel configuration have been developed. These filters, described for example in the co-pending, commonly assigned U.S. patent application of W. Cutler et al., Ser. No. 09/211,134 filed Dec. 14, 1998 (that application being expressly incorporated herein by reference), can provide true cyst reduction performance at gravity flow filtration rates of at least 200 ml/minute. By "cyst reduction" in a filter, filter system, or filtration process is meant a filter, filter system, or process capable of providing at least 99.95% removal of 3-4 .mu.m particles from a raw water source when tested in accordance with NSF Standard 53, Drinking Water Treatment Units--Health Effects (September 1997).
Although filter designs and materials capable of effective cyst reduction exist, significant problems remain concerning appropriate methods and designs for incorporating such materials or filters into effective, gravity-fed water carafe purification systems. This is because cyst reduction pertains to a health concern, rather than a lesser concern about water taste and odor.
Any successful carafe filtration system must first prevent the mixing of unfiltered water with water already treated by the filter. Current carafe systems are not designed for cyst filtration. For example, that the seal positioned between the filter cartridge and the carafe inlet reservoir on a typical commercial carafe is typically a loose taper fit. Such seals readily allow unfiltered water to enter the filtered water chamber via the pour spout, reservoir/filter seal, and/or reservoir/carafe seal. In these designs, therefore, contamination of the raw water with unfiltered water can occur during filling, during the filtration process, or during pouring. Obviously, only minor leaks of raw water to the filtered water reservoir are needed to entirely negate the health benefits to be derived from the use of a cyst reduction filter element, no matter how effective the cyst removal of that element may be.